Help me understand Turbo

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4RNB

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4RNB
So in my constant perusal of classified ads, I see that a turbo equipped aircraft of the same make and model lists cruise speeds faster than non turbo similarly equipped aircraft. My impression is that this increase speed is really only obtained at higher altitudes Is this correct?

Also, in general, I see that folks say to go turbo route for long distances where these increased speeds pay off better.

Ignoring the maintenance needs, how do people realistically choose turbo vs non turbo?

And for those that have turbo, if the speed really comes at higher altitudes, is there a trade off for distance that staying lower and slower makes sense from a fuel economy perspective? Or does any fuel burnt in climb payoff during descent?

How have you evaluated turbo vs non turbo purchase decisions? For those that have turbo, are there flight planning decisions pertaining to fuel burn and distance flown that one considers for each flight?

C182 is the specific plane model I follow.
Thank you for correcting any knowledge deficiencies I have...
 
My plane is normally aspirated. At 10k feet, wide open throttle, I only saw 21" of manifold pressure on a recent flight, my engine was probably only making 65%, and climb performance rolled off.

A turbonormalized engine would boost that back up to 30" and you'd be making the same power at altitude as you would at sea level, and you could keep climbing.

A turbocharged engine would boost that above ambient pressure, and you'd be making more power than an equivalent normally aspirated engine.

So, turbo=more power at altitude=faster, and better climb performance. Also, more maintenance. Higher altitude also means higher TAS, maybe more favorable winds, and also lets you go over those pointy rocks out west. Also, you may need oxygen.

As for the various trades... It Depends(tm).
 
All correct. Normally aspirated piston engines power rapidly falls off in the ascent.

In terms of overall flight efficiency : time to climb wind at altitude, cruise ground speed etc all are considerations..if you have turbo you can go higher faster so that give you options in this matrix of numbers you don't have with normally aspirated. If you did lots of short hops a turbo may not make a lot of sense.

Also capex vs opex costs are considerations

Are you looking to purchase your next aircraft and if so what sort of mission profile would be typical? What is you preferred capital outlay and how much is you annual budget ongoing
 
Your engine needs certain amount of air to function optimally. As it happens the higher you go there is less and less air available - so turbo is just there to “bring back” some of that air via tricks like compression etc …

So you are not really going faster up there, you just maintain the same efficiency at altitude while others go slower ….
 
Something to think about is where you live and will be flying. I live in northeast so I don’t have to deal with topping mountains or high elevation take offs with really high DA where the turbo would help. If I lived in the west with higher elevations I think it would be much nicer to have.
 
4RNB said:
My impression is that this increase speed is really only obtained at higher altitudes Is this correct?
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You need to look at the cruise performance tables and compare. It's been a while, but for example, I recall uniformly higher cruise speeds in the turbo Arrow than in the normally aspirated ones.
 
Warmi said:
Your engine needs certain amount of air to function optimally. As it happens the higher you go there is less and less air available - so turbo is just there to “bring back” some of that air via tricks like compression etc …

So you are not really going faster up there, you just maintain the same efficiency at altitude while others go slower ….
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I always had a visual oi someone shoving lots of food into their mouths with both hands.
 
I was thinking about this before I bought my plane. I think if you will be at higher density altitudes a fair amount, the turbo makes a lot of sense. I am in the midwest, so other than the occasional trip out west, I wouldn't really be taking advantage of a turbo. Most of the time I just putz around the area at 4-6k. Also, to really utilize the turbo, you will be sucking oxygen a lot, and that is just another thing to worry about. Again fine if you need to fly higher a lot, but I didn't really want to deal with it.

That said, turbo normalized bonanzas are pretty awesome!
 
first there are two methods of turbo charging. turbo charge and turbo normalized. as stated here, turbo normalized allow rated power to a higher altitude. so at sea level, the speeds will be the same. as you climb the N/A version will loose power. turbo normalized aircraft are advertised with a cruise speed at a higher altitude to make the numbers bigger than the N/A version and rightly so, since who cruises at sea level.
a turbocharged engine will make more boost at sea level than local pressure. so, more air, more fuel, more power and more speed. the sport guys at reno are running massive amounts of boost, and massive amounts of HP. that's also why they go BOOM! more often.
 
I live in the Southwest US and elevations of the airports we frequent vary from sea-level to 7,000’. Without a turbo to help out, Flagstaff/Gallup on a warm day can be scary and/or not able.

In my case, I fly a turbocharged 540 and I can develop 65% power at FL200. The thin air helps boost that TAS.

We fly lots of long trips (3+hr) and it makes the climb/descent to the teens more practical. Heck, since I keep my 1,000’ft/min for a good long time, I seldom cruise below 10,000.

Maintenance differs from engine to engine based on wastegate designs, locations and other factors.
 
Rgbeard said:
Without a turbo to help out, Flagstaff/Gallup on a warm day can be scary and/or not able.
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Yes it can. Over the years we have had a number of planes stop here in Gallup for fuel then decide to spend the night and plan a 6am departure.

Currently at 9:15am in Gallup, temp 48f, density altitude 7100.

Summer time the D/A can be 9000 to 10,000 in the daytime.
 
benyflyguy said:
Something to think about is where you live and will be flying. I live in northeast so I don’t have to deal with topping mountains or high elevation take offs with really high DA where the turbo would help. If I lived in the west with higher elevations I think it would be much nicer to have.
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what about just for the faster cruise speeds?
 
When I first started flying turbocharged airplanes regularly (in this case a Turbo Saratoga), I immediately appreciate the "availability" or more altitudes for cruise. Even in flat, low, Oklahoma and surrounding states this opened up a lot of flexibility. A NA airplane generally is most efficient around 7,000 MSL. Above that, power starts to drop off faster than TAS is gained. So a NA airplane's cruising "window" is something like 4000 to 8000. Well, that's where a whole lot of the bumpy cumulus clouds are, making for a rough ride. Even without having to use oxygen, a turbo expands that to 12000 or so, which will often (but not always) get you above a lot of the hot, bumpy air.

It also gives you more flexibility to avoid headwinds. Often, if the wind is a headwind at 5 or 6000, it swings around a little by 12000 and maybe becomes just a quartering headwind. And, of course, you have more altitudes to find a good tailwind.

It's all about flexibility. You can cruise at 4000 if you want, or go to 12000, or if you really want to, put on oxygen and go much higher. You don't have those options (realistically) with a NA airplane.
 
Are you instrument rated? Is there icing in your area? Are you flying far enough to make the climb worth it?
 
GeorgeC said:
Are you instrument rated? Is there icing in your area? Are you flying far enough to make the climb worth it?
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if not clear, I am trying to figure out the trade offs to consider your questions like am I flying far enough to make the climb worth it. For turbos, what distance makes it worth it?
 
Another consideration not mentioned yet, unless I missed it, is the safety aspect that a better climb rate affords. Say if one encounters ice and chooses to climb, the turbo will benefit here.
 
4RNB said:
if not clear, I am trying to figure out the trade offs to consider your questions like am I flying far enough to make the climb worth it. For turbos, what distance makes it worth it?
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You haven't provided any details, so the answer continues to be It Depends(tm). It could be worth it for as little as a couple hour flight, but say you're in the northeast and you're not instrument rated and there's an overcast, or you are instrument rated but it's winter and there's icing; you may not have the opportunity to take advantage of your would-be turbo 182.
 
1978 is a few years back, but the density altitude issues at mountain west airports have not changed.

Wife and I flew from Lexington, Nebraska in a Cessna 172, with ONE medium bag, and some snacks.

We refueled at Wray, with a density altitude 2000 feet higher than airport altitude. Cruise was at DA 13,500 to get out of the worst of the thermal turbulence.

Landing at Colorado Springs, the density altitude was 13,000 feet on the runway. A longer than normal run resulted from the stall speed being at a much higher ground speed. It was only mid afternoon.

Departing on a later day, at 7 AM, Fueled at 10 gallons less than full, DA 8,000 feet, counted the markers til rotation, 1,200 feet. Max rate of climb 300 FPM after level acceleration. Crossed the end of that very long runway at a very modest altitude. All luggage and other carry-ons weighed 40 pounds.

A non turbo plane is severely limited out there in the summer, and the summer is a lot of months. Fun trip, but well prepared, and scheduled. No departures after noon, no long legs, and no full tank departures above DA of 8,000 feet.

Gallons per hour are lower due to less air density and limited manifold pressure with even more gain from proper leaning, and the higher adjusted true air speed give longer legs with a given fuel supply. Going downhill out of Colorado Springs, we did an hour and 3/4s with a modest indicated airspeed for best range.


Our two young sons traveled by ground transportation, and met us there. Their grandfather attended a reunion of his WW 2 unit, the 345th Fighter Squadron, P 47 Thunderbolts. They flew from North Africa into Italy.
 
When I purchased my plane....it happened to have a turbo. I didn't seek it out. Since this, I'd think twice if my next one didn't have a turbo. I really like having the option to go high and climb there at a nice rate.

Do I use the turbo....nope, not like it should. I rarely go above 7-8,000 feet. But, I have options. Has it cost me more? I don't think so. I've replaced a v-band clamp and had to do a few tweaks....but I've learned how to maintain my engine and I do all the maintenance. If I needed a shop to perform maintenance it may cost more....but it shouldn't. Mine has been relatively maintenance free.
 
Checkout_my_Six said:
When I purchased my plane....it happened to have a turbo. I didn't seek it out. Since this, I'd think twice if my next one didn't have a turbo. I really like having the option to go high and climb there at a nice rate.

Do I use the turbo....nope, not like it should. I rarely go above 7-8,000 feet. But, I have options. Has it cost me more? I don't think so. I've replaced a v-band clamp and had to do a few tweaks....but I've learned how to maintain my engine and I do all the maintenance. If I needed a shop to perform maintenance it may cost more....but it shouldn't. Mine has been relatively maintenance free.
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It should be...ya just OH'd it!
 
I have flown between ND and the southwest (AZ, NV) a few times. This would be easier with a turbo to gain some leeway above layers of icing when the MEA is already 12,000 or 14,000, but the real upgrade would be pressurization. Otherwise I just plan a route around weather with the aim of needing no or minimal time with the oxygen turned on, the same as I would with a turbo.
 
Warmi said:
So you are not really going faster up there,
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Only if you are talking IAS. You DEFINITELY gain in TAS.

My airplane, a turbo Mooney, flies pretty much the same IAS at the same power setting below 10000 versus in the teens. But the TAS can be 20 knots faster.
 
4RNB said:
if not clear, I am trying to figure out the trade offs to consider your questions like am I flying far enough to make the climb worth it. For turbos, what distance makes it worth it?
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If you have Fore Flight, set up a profile for a turbo airplane. FP some trips and on the flight plan page you can click on altitude it and it will give you a table with cruise altitudes and fuel and time for each one. You will see that many times the fuel burn and time are similar for a given trip at various altitudes, but long trips start making a difference. And then add in winds, it can make a HUGE difference, even on a fairly short trip.
 
Have over 3000 hours behind turbo engines on both coasts. If it's an option for the aircraft you have or seek, would suggest getting the turbo version. Main reasons are: always have maximum rated horsepower with accompanying better climb rate on take-off regardless of density altitude, cruise in the cooler smooth air above the clouds, and enjoy higher TAS above about 10,000' due to the thinner air whilst still cruising at 65-75% power.

Primary downside is must be comfortable using oxygen more of the time, though even < 10,000' the benefits are worthwhile, particularly in summer when DA is high even on the ground. Some additional maintenance costs, but worth the price. For example, v-bands need periodic replacement, some exhaust components may need more frequent replacement, and one will probably want to overhaul the turbo components (turbo, waste gate and controller) at engine overhaul.

Don't get hung up on turbo-normalized (TN) vs. turbo-charged (TC). They both have the same parts and work the same way. The TN systems are often found on engines that were not initially certified as turbo-charged and thus are limited to the maximum induction manifold pressure they can make as a non-turbo'd engine (around 31'' Hg). In a TC system the certification allows the engine to make more than its previous SL MP - about 32-41" Hg typically.
 
FORANE said:
Another consideration not mentioned yet, unless I missed it, is the safety aspect that a better climb rate affords. Say if one encounters ice and chooses to climb, the turbo will benefit here.
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Transitioning over the Sierras at 16,500 msl I climbed to 17,500 msl at 800' per min at 80% power with my turbo-normalized 182P. Was on flight following at the time and ATC asked to confirm I was actually a 182. :7)

I found flying 5000-6000 AGL over mountain peaks smoother and safer. Also while other guys are on the ground due to high density altitude, I'm able to leave at max gross weight.

The turbo STC is rated for 3 mins at 29" and continuous at 27". I'm usually operating over-square with higher manifold pressure and lower RPM. Real benefits in fuel economy and engine longevity. Just majored the engine which went WAY over TBO.

The Rajay STC is certified to 25,000 msl, though I've only flown her to 18,500 msl.

@Pinecone idea to set-up turbo profile in Foreflight is excellent, or just look at the flight data charts on an online POH. Easy to get data for a turbo 182T and normally aspirated 182. I see 112 KIAS up high with 162 KTAS. That books close to a T182T.
 
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Steamflyer said:
In a TC system the certification allows the engine to make more than its previous SL MP - about 32-41" Hg typically.
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But that is normally paired with lower compression pistons.
 
Pinecone said:
But that is normally paired with lower compression pistons.
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Built and paired with whatever components needed to pass certification at maximum MP allowed. May have a time limit for some engines as well. May have fuel flow requirements under certain conditions, etc. Detonation margin requirements often does lead to lower compression ratios. There's no thermodynamic free lunch, but a well managed turbo will happily run to TBO and beyond.
 
Pinecone said:
If you have Fore Flight, set up a profile for a turbo airplane. FP some trips and on the flight plan page you can click on altitude it and it will give you a table with cruise altitudes and fuel and time for each one. You will see that many times the fuel burn and time are similar for a given trip at various altitudes, but long trips start making a difference. And then add in winds, it can make a HUGE difference, even on a fairly short trip.
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I believe this is only true with the "Performance Plus" level, or whatever it's currently called. For the basic level of service, you can only enter one cruise speed and it applies to all altitudes. The Performance Plus level knows that TAS gets higher with altitude for a turbocharged airplane, and you can see those results.
 
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